Cagliari Chief Prosecutor Mauro Mura told reporters that as well as planning to launch attacks in Pakistan and Afghanistan, as earlier reported, the suspects may also have been aiming to target the Vatican.

Police conducted raids across Italy on Friday, targeting 18 people suspected of links with al Qaeda. Some were arrested, including the group's suspected spiritual leader, but others were believed to have left the country.

"We don't have proof, we have strong suspicion," said Mario Carta, head of the police unit leading the investigation said when asked for more details on a possible attack against the seat of the Catholic Church.

He said that, in intercepted telephone calls, investigators had heard the suspects say they would launch a "big jihad in Italy," conversations that also suggested a target might be the Vatican.

All the suspects are Pakistanis or Afghans, Carta said earlier, adding that the operation was still in progress.